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Dam Safety Program

The U.S. Army Corps of Engineers’ (USACE) Detroit District Dam Safety Program uses a risk-informed approach to manage its portfolio of 10 dams, (9  on the lower Fox River in Wisconsin and the Soo Locks), with public safety the number one priority. This robust risk-informed approach is a best practice adopted to develop balanced and informed assessments of the safety of our dams and to evaluate, prioritize and justify dam safety decisions.

Critical to an effective safety program is, of course, the focus on public safety, but it also requires continuous and periodic project inspections and evaluations.  The Dam Safety Program seeks to ensure that USACE owned and operated dams do not present unacceptable risks to people, property, or the environment, with the emphasis on people. 

 

 

Program Information

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The objectives of USACE dam inspections are to:
  • Ensure the dam system will perform as expected.
  • Identify deficiencies or areas that need monitoring or immediate repair.
  • Continuously assess the integrity of the dam in order to identify any changes over time. 
  • Collect information in order to make informed decisions about future actions.
  • Determine if the dam is being properly operated and maintained.
  • Determine if the local sponsor is in compliance with the project partnership agreement, if applicable. 

USACE conducts two types of dam inspections.  The first one is the Annual Inspection, which is performed on an annual basis to ensure the dam is being properly operated and maintained.  The Periodic Inspection is the next level of inspection and is conducted by a multidisciplinary team led by a professional engineer.  It includes a more detailed, comprehensive evaluation of the condition of the dam and will be conducted every five years.  Components of the Periodic Inspection include evaluating annual inspection items; verifying proper operation and maintenance; evaluating operational adequacy, structural stability, and safety of the system; and comparing current design and construction criteria with those in place when the dam was built. 

In 2005, the USACE started Screening for Portfolio Risk Analysis (SPRA).  This analysis screened every one of the approximately 692 dams in the USACE inventory based on available information, to expeditiously identify and classify the highest risk dams requiring urgent and compelling action (Dam Safety Action Classification Classes I and II Dams).  This screening has yielded a clear but basic understanding of where the greatest risks and priorities are located.

Completing SPRA has allowed USACE to develop a Portfolio Investment Plan for more than 300 dams within the portfolio determined to be “actionable,” or posing moderate to extremely high risks.

The Dam Safety Action Classification System (DSAC) is intended to provide consistent and systematic guidelines for appropriate actions to address the dam safety issues and deficiencies of USACE dams.  USACE dams are placed into a DSAC class based on their individual dam safety risk considered as a combination of probability of failure and potential life safety, economic, environmental, or other consequences.  The DSAC table presents different levels and urgencies of actions that are commensurate with the different classes of the safety status of USACE dams.  These actions range from immediate recognition of an urgent and compelling situation requiring extraordinary and immediate action for unsafe dams through normal operations and dam safety activities for safe dams.



DSAC Class I (Urgent and Compelling) – Dams where progression toward failure is confirmed to be taking place under normal operations and the dam is almost certain to fail under normal operations within a time frame from immediately to within a few years without intervention; or, the combination of life or economic consequences with probability of failure is extremely high. 

DSAC Class II (Urgent) – Dams where failure could begin during normal operations or be initiated as the consequence of an event.  The likelihood of failure from one of these occurrences, prior to remediation, is too high to assure public safety; or, the combination of life or economic consequences with probability of failure is very high.

DSAC Class III (High Priority) – Dams that have issues where the dam is significantly inadequate or the combination of life, economic, or environmental consequences with probability of failure is moderate to high.

DSAC Class IV (Priority) – Dams are inadequate with low risk such that the combination of life, economic, or environmental consequences with a probability of failure is low and the dam may not meet all essential USACE engineering guidelines.

DSAC Class V (Normal) – Dams considered adequately safe, meeting all essential agency guidelines and the residual risk is considered tolerable. 

Risk comprises the following three elements:  the likelihood that natural events will take place, the performance of the infrastructure during these events, and the consequences of poor performance or failure.  Risk allows USACE to look at the project in terms of its purposes; ecosystems; constrained budgets; the uncertainty of future events and current knowledge; past design decisions; and combinations of these factors and make sense of it all.

USACE takes a multi-faceted approach to managing risk of the dams it operates and maintains.  Risk-informed decisions integrate traditional engineering analyses with estimations of risk through experience-based engineering judgment.  Dam safety risk-informed program is managed with three main components: risk assessment, risk management, and risk communication.

Risk Assessment
A risk assessment is a systematic approach to quantify and describe the hazard, likelihood of something going wrong, and consequences if something goes wrong.  It is used to define safety issues, evaluate remediation options, and measure effectiveness of repairs.  It enhances decision-making for setting short and long-term priorities for studies, investigations, and repairs.  Risk assessments are performed on a continuous basis because risk can change over time.

A national screening-level risk assessment process began in 2005 in which USACE categorized dams among five Dam Safety Action Classifications (DSAC) based on relative risks.  This allowed USACE to identify dam safety issues and prioritize actions and funding according to those risks.

Risk Management
Risk management is the process of problem finding and initiating action to identify, evaluate, select, implement, monitor and modify actions taken to alter levels of risk, as compared to taking no action.  The purpose of risk management is to choose and prioritize work required to reduce risk.

USACE uses routine and non-routine activities to make risk-informed management decisions. 

Routine: Routine activities include monitoring of instrumentation, inspections and assessments.  Instrumentation monitors critical components of the dam.  Engineers regularly inspect projects for structural and operational integrity and identify potential problems and issues.

Non-Routine: An incident or special event at a dam or a safety concern during routine activities triggers non-routine activities.  This may include an issue evaluation study to determine the extent of the dam safety issue.  Concurrently, interim risk reduction measures (IRRM) to lower risk are used until permanent measures can be put in place and may include lowering reservoir pools, stockpiling emergency material, updating emergency action plans and inundation maps, and increasing instrumentation and monitoring.  If permanent action is needed, a modification study determines options and aids prioritization.

Dam Safety Modifications: Many dam safety issues can be addressed through normal maintenance. Some, however, require extensive and expensive modifications.  A risk-informed alternative analysis determines the most cost-effective measures to reduce the project risk as low as practicable.  Modifications can take several years and include such actions as foundation cutoff walls, anchoring dams, and placing seepage berms.

Risk Communication
Risk communication is the open, two-way exchange of information and opinion about hazards and risks leading to a better understanding of the risks and better risk management decisions.  USACE provides risk information on a project basis to affected stakeholders and the public.  An informed and engaged public that better understands risk can contribute to the evaluation of risk reduction options, and take appropriate action for their safety.